Contact terminal structure



May 2,1944. J. F. EBERT 2,347,815

CONTACT TERMINAL STRUCTURE Filed Sept. 12, 1942 \\\\\\\\i Z fA Ummm sary in this Patented May 2,'1944 CONTACT TERMINAL STRUCTURE Joseph F..Ebert, Hollis, N. Y., assignor to Allied Control Company, Inc., poration of New York Application September 12, 1942, Serial No. 458,175

(Cl. o-166) 3 Claims.

'I'his invention is directed to contact terminal structures particularly adapted for use in various electrical apparatus such as relays.

It has been customary in making contact terminals to provide a metallic member on which is formedfor to which is secured, a suitable contact face adapted to make contact with another member for the transmission of current. It has also been customary to secure to the contact terminal a. lead-in wire which carries the current to or from a suitable source through the terminal and the contact to complete the circuit. Such lead-in wires were secured to the terminal`V by soldering, welding, or the like. It has been necesoperation to provide a soldering flux, or the like, to prepare the metal surfaces for the soldering or similar operation.

Unless one took great care in the operation, the flux when contacted by hot solder or a hot soldering iron would flow into contact with the contact button, and by capillary action, would rise and cover the contact face. This, of course, injuredthe contact area and prevented the full flow of current across the contacts. Therefore, it was necessary to clean the contact faces of the terminals which required delicate operations in order to remove the flux without injuring the contact faces.

In the case of small size and delicate relays, the problem was substantially accentuated. It became still more difficult to prevent the free flow of #ux and consequently, the operation of soldering lead-in wires became quite a troublesome one.

The present invention is designed to overcome this difficulty and to provide a contact terminal structure wherein the flow of liquid flux will be incapable of affecting the contact faces thereof.

It is also an object of the present invention to provide a structure wherein ux may be allowed to iiow freely without taking any unusual precautions, while at the same time, avoiding the danger of dirtying the contact faces.

In practicing the present invention there is `provided a terminal member, as usual, having means for securing the same to a suitable insulating support and also having means for attaching a lead-in wire thereto. A-contact button is provided, but the structure thereof is such that the meeting faces of the button and terminal define an area which is less than the area of the contact face itself. Also, the dimensions of the contact area are less than the dimensions of the contact face. 'By reason thereof, there is an undercut portion at the meeting faces which acts as a trap for liquid flux as it flows on the surface New York, N. Y., a corof the terminal. The undercut portion is usually in the contact button itself, but may be in the face of the terminal or partly in each. The shape of the undercut portion is usually an acute angle, but it may be of any other desired form.

The essential feature of the structure is that there is a sufficient amount of undercut and the undercut is of such shape that it prevents the raising of liquid from the terminal base by capillar'y action, and thus prevents the dirtying of the contact face of the button. By reason of the reentrant angle, when liquid ux enters into the undercut portion, surface tension is set up, forming a meniscus, which exerts a sumcient force to hold the flux within the undercut portion.

In the accompanying drawing constituting a part hereof and in which like reference characters indicate like parts:

Fig. i is a side elevational view of a dontact :erminal structure embodying the present invenion;

Fig. 2 is a top plan view thereof;

Fig. 3 is a vertical cross-sectional view taken along the line 3 3 of Fig. 1 and showing more specifically the contact faces of terminal and base;

Fig. 4 is a fragmentary enlarged longitudinal cross-sectional view showing liquid flux and the manner in which it is prevented from rising to the contact face; and

Fig. 5 is a. similar view of a modied form.

The terminal base I consists in the embodiment shown, of a at strip of metal having an opening 2 at one end thereof for the introduction of a screw to hold the base to an insulating member.

An opening 3 at a central portion of base l receives the shank of a contact button 4,'the upper faceof which is flat and is adapted to cooperate .with a similar button on a' contact arm (not shown). The opposite end 5 of the shank is upset to anchor the contact button 4 permanently on base l. y

At the opposite end of base l is an opening 6 through which a lead-in wire 'l is adapted to be inserted, the free end 8 of said wire being bent over to hold it temporarily in position. The face opposite the contact face of button 4 is undercut as shown at 9 to form a re-entrant angle. The undercut as seen from the several figures, is circumferential and is formed completly/A around button 4. This provides a face i0 in contact with base l, the face Hl being of substantially less area than the contact face of the button.

In the operation of attaching a lead-in wire,

- dering placed in. the position shown in Fig. 4, Iiux is placed on end 8 of wire land on the adjacent parts to be joined. During the soloperation the ux is heated by the solder or soldering iron and some of it tends to flow along the surface of the contact 4 and enters the undercut 9 as indicated the parts are terminal, toward the at II in Fig. 4. By reason of surface tension,

the flux is held within there-entrant angle and forms a meniscus I2, the surface tension of which is so great as to prevent any liquid from creeping up the side I3 of button 4, and thus keeps the contact face thereof clean. As a result of the soldering operation, the wire 8 is -rmly attached to the terminal I bythe body of solder I4.

Although I have described my invention, setting -forth a single embodiment thereof, it Will be apparent to those skilled in the art that various changes in the detailsk of construction may be made within the scope of the invention. For instance, the terminal base may be of any size or shape or of any material desired. Contact buttonA 4 need not be circular in outline, but may be of any desired shape, and the contact not necessarily be perfectly fiat. The re-entrant angle 9 has been shown as an acute angle, but such re-entrant portion need not be made on straight lines, as curved surfaces will also accomplish the desired result. It is also unnecessary to have a side I3 at right angles to the contact face, as the entire sideportion4 of button 4 may be undercut. Also, the reon the button. changes may be made in the details olf-construction within the spirit of the invention, and the invention is therefore to be broadly construed and not to be limited except by the claims appended hereto.

What I claim is:

1. A contact terminal structure for electrical apparatus comprising a terminal base, a contact button secured to said base, the contact face of said button being spaced from said base, the button contacting with said spaced from said base, the

JOSEPH F.v EBERT. 

